The history of natural selection, in 7 minutes

The idea of evolution by natural selection is, for me, probably the most beautiful idea in biology

There's two things we have to think about here. One is evolution itself

Do animals and plants evolve? And the second is, what is the mechanism by which it takes place

The idea that animals and plants might evolve is actually quite old

Even Aristotle had some thoughts about it. But particularly in the 18th century, there were a number of people who speculated

looking at fossils and so on, that animals and plants had evolved over time

But it took Charles Darwin in the middle of the 19th century

to come up with a mechanism, evolution by natural selection. And he came to this position because of a five-year voyage he took

in a small Royal Naval boat called the Beagle that went round the world

and he collected animals and plants and birds and studied the geology

made lots of natural history observations. And this eventually led in the 1840s to his idea

He didn't publish it till 1865. And it provided a mechanism by which animals and plants could evolve

And really, you could get design without having a designer. Now, how is that possible

It's a very clever idea. And it's based on the genes that I've already talked about and cells, really

and what he speculated was that all living things have hereditary material He didn know about genes but he speculated that they had hereditary material

That if this hereditary material had some differences that resulted in the living thing

living organism being different, then it is possible that what was produced

was perhaps a plant or an animal that could grow faster or produce more offspring

And that would mean that in the next generation, there would be more of that particular variant

And if it was advantageous in the environment in which it found itself

then it would eventually take over the whole population. So you get a change from one type of organism into one that was a bit different

I sometimes think of a very simple model just to explain that. Imagine a single-celled organism which had a red coat outside the cell or a yellow coat

Let's say that the red coat got eaten by some other living organism

Then if there was a mutation which resulted in the red coat turning into a yellow coat

then the yellow coated cells would survive better than the red coated ones and as a consequence they

would take over the population and that's just a very simple example of evolution by natural

selection but it's also built on the ideas that I've been talking about it's built on the idea of

genes and the fact that genes determine the properties of cells and if you have genes

determining the properties of cells and the genes show some variability, then you will

simply get evolution by natural selection And this was the idea Darwin had He didn know about genes but he did know about hereditary material

And this has been a revolutionary change in our understanding in biology

because what it leads to is a better-designed living thing without having a designer

It can occur just randomly by selecting naturally for those changes that are more advantageous for that living thing. It really

truly is a beautiful idea. One of the consequences of evolution is that we're related by descent

because if we all can trace back our ancestors to a common place then every living thing

on this planet is related. This is rather profound, really. The relatedness of all living things

and particularly of humans to other life forms, was brought home to me in a very special way

almost spiritual, when I was trekking through a Uganda rainforest looking for gorillas

And we came across a whole family of them, 20, 25 of them. I sat down behind a tree. I was a

little bit separate from the rest of my group. And then this very large male gorilla sat down in

front of me and looked at me, deep brown eyes. He put out his arm, he bent down a sapling tree

two, three, four inches in diameter. I'm sure he was telling me, you know, I can do this

I'm not sure you can do this. But sitting there, just looking at him, seeing the similarities

his deep brown eyes and they were really staring at me. It just looked like we were having a conversation somehow He sat and looked at me for a while Then he climbed up the tree and then he peed all over me

So I don't really know whether he was trying to put me in my place

But for sure, it was a magnificent interaction. Here I was, almost talking

to a sort of relative diverged five million years ago, 10 million years ago

And it made me think of the deep connection between all life on this planet. It's just that we diverged further and

further back. And that experiment that I described of taking the human gene and putting it into a

yeast cell and showing that that human gene could control the reproduction of the yeast cell just as

well as it could control a human cell, even though they diverged 1,500 million years ago

is another example of the extraordinary similarity between living things. And I think about this

quite a lot because doesn't it mean if we're related to every living thing on the planet

do we not have a special responsibility for every living thing on this planet

they are really all our relatives. Do we not really have a responsibility to be a steward

for all animals, plants, fungi? We have a responsibility for them. And it's the best argument I've seen in an abstract sort of way

that we should take care of every living thing that we can on this planet

because we're related to every living thing on the planet. They are our relatives

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